For many years, the normal type of dental chair was one in which a seat was mounted upon a base and hydraulic or other equivalent means were employed to raise and lower the seat relative to the base. A back was pivotally connected at its lower end to the rear end of the seat and was adapted to be moved from substantially upright position to a rearwardly and angularly inclined position relative to the horizontal. A foot rest, which was attached to the outer or lower end of a leg rest also was included, the leg rest being connected pivotally to the front end of the seat and, at least in recent years, when the back was moved from upright to inclined position, the leg rest was extended from perpendicular, depending position, to an angularly and forwardly extended position and the foot rest was usually moved from a perpendicular position relative to the leg rest to an outwardly extending substantially horizontal position.
When a patient was to be seated in a chair of the foregoing type, he usually could stand upon the foot rest and somewhat turn around to a limited extent while being seated in the chair. Chairs of this type, however, in the lowest position thereof, were relatively high and normally required a dentist to stand while performing dental operations in the oral cavity. In recent years, however, it has become very popular for a dentist, as well as a dental assistant, to be seated while operating upon a patient, thereby increasing the comfort to a dentist and dental assistant. However, this necessitated the development of dental chairs and the like which had a seat closer to the floor level than the seats of chairs which were popularly in use prior to that time. As a result, one very popular type of chair which was developed comprises the subject matter of U.S. Pat. No. 3,774,965, to Brandt et al., dated Nov. 27, 1973 and U.S. Pat. No. 3,823,979, to Davis, dated July 16, 1974. In these patents, however, the leg rest extended forwardly from and actually constituted and integral part of the seat and was rigid therewith. In order for a patient to be seated upon a chair of this type, it was necessary for the patient initially to sit upon the seat sideways and then raise his legs and turn himself through a substantially 90.degree. arc in order to dispose his legs upon the horizontal extending leg rest of the chair seat. Hence, while these chairs have backs pivotally connected to the rear ends of the seats, when the back is moved from upright to inclined position, no corresponding movement of the leg rest occurs.
Another chair manufacturer, in attempting to adapt their products to the more modern mode referred to above, developed a chair in which the leg rest, while a continuation of the seat, nevertheless, was flexibly connected therewith in order that the outer end thereof might at least be moved through a limited angular arc from a downwardly inclined position of about 45.degree. to the horizontal, to a substantial horizontal position. Such chair comprises the subject matter of U.S. Pat. No. 3,486,789 to Taylor et al., dated Dec. 30, 1969. This chair complied substantially with the so-called "low profile" mode which was being introduced to the dental profession at the time of such development of the chair, but in order to have a patient seat himself in the chair, such seating initially took place sideways with respect to the seat and then the patient had to move himself through an arc of about 90.degree. to dispose his legs upon the leg rest, when the latter was in the initial position.
Particularly in regard to female patients, many of whom wear short skirts at the present time, as well as for other purposes set forth in detail hereinafter, the seating of patients upon chairs in which the leg rest is either rigid with the seat or a substantial continuation thereof, as in the Taylor et al. patent, room for improvement has been found to exist by the inventor of the invention comprising the subject matter of the instant application, details of which are set forth hereinafter.
In regard to the feature of moving a dental seat and the back connected thereto relative to a leg rest in a chair of the type normally employed by dentists or similar corresponding uses, it has been found that no very close development has occurred as far as the patented art is concerned. It is well-known that in the art of mechanic's or draftsman's chairs, particularly those which have a seat disposed at an abnormally high location with respect to a supporting floor, such as chairs somewhat resembling bar stools in height, it has been somewhat common to provide foot rests extending outwardly from the supporting pedestal for the chair seat so that a person seated upon this chair or stool conveniently could at least support their heels upon such foot rests. Typical examples of this type of chair or stool are found in the following exemplary patents:
U.S. Patent No. 1,590,240 Gorton June 29, 1926 1,723,363 McArdle Aug. 6, 1929 2,437,940 Cramer et al Mar. 16, 1948 2,439,869 Sharp April 20, 1948 3,820,844 Fortnam June 28, 1974
Particularly when tilting the back of a chair, such as one of the types normally employed by dentists and the like, it has been customary for a number of years to raise the front portion of the seat a limited distance when the back is moved from substantially upright to a rearwardly inclined position. Such movement of the forward portion of the seat to a higher elevation under such circumstances has been accomplished in various ways, many of which are relatively complex, such as illustrated in the following exemplary patents:
U.S. Patent No. 2,714,922 McKibban et al Aug. 9, 1955 2,859,799 Moore Nov. 11, 1958 3,056,629 Fletcher Oct. 2, 1962 3,142,509 Ehrke et al July 28, 1964 3,381,997 Fritz et al May 7, 1968 3,804,460 Leffler April 16, 1974
Accordingly, it has been found that there is room for improvement in regard to structures for tilting the seat upwardly at the forward end when the back is inclined toward a rearward position, and such more simple improvements are set forth hereinafter.